Major emphasis will continue to be placed on defining macrophage heterogeneity among peritoneal macrophage subpopulations separated on the basis of density. We have achieved basic information with C. parvum macrophages, and this information will now be obtained for resident and thioglycollate elicited macrophages. In addition to the current assays for ectoenzyme phenotypes and antitumor activity, we plan to determine permissiveness of the subpopulations for HSV. Our preliminary results with total peritoneal macrophage populations revealed that resident and C. parvum macrophages are almost completely resistant to HSV infection, while there was erratic growth in the thioglycollate macrophages. Determination of susceptibility of separated subpopulations may show that certain populations have enhanced susceptibility while others are as resistant as the resident macrophage population. Our research currently is focussed on separation on Ficoll discontinuous density gradients. It has taken considerably longer than expected to get the Beckman elutriation centrifugation system in Dr. Miller's laboratory functioning well on a routine basis. We expect to perform experiments with the elutriator to confirm that results similar to Ficoll separation are obtained and then move completely to the elutriator. In addition, we plan more studies of the separated subpopulations using the FACS cell sorter analysis capability. The second thrust of the research will be directed at macrophage cell lines, delineating biochemical markers and permissiveness for virus infection. The continuing work with J774.1, WEHI-3 and PU5-1.8 mouse macrophage cell lines has been detailed above. We are now initiating studies with the immature human macrophage cell line, U937. This cell line, upon treatment with lymphokine, "activates" in regard to ADCC activity and phagocytic activity. We are documenting the changes that occur in ectoenzyme phenotypes and permissiveness for HSV during this progression. Laura Googin will be responsible for this latter project.